Double purpose gas filled tube



Oct. 29, 1957 w. D. CALDWELL DOUBLE PURPOSE GAS FILLED. TUBE 2 Sheets-Sheet 1 Filed Feb. 15 1952 Ffzv. 2.

LUHCHE D CQLDLUELL,

INVENTOR Oct. 29, 1957 w. D; CALDWELL 2,811,310

DOUBLE PURPOSE GAS FILLED TUBE Filed Feb. 15, 1952 2 Sheets-Sheet 2 59 as 58 o o 0 I1- f 07 6 n 48 2 55 'uJw'cuE D. CQLDLUELL.

INVENTOR.

United States Patent i DOUBLE PURPOSE GAS FILLED TUBE Wyche D. Caldwell, Sherman Oaks, Calif., assignor to Telecomputing Corporation, Burbank, Cahf., a corporation of California Application February 15, 1952, Serial No. 271,825 24 Claims. (Cl. 235-92) This invention relates to a double purpose gas filled tube such as a thyratron and more particularly to a thyratron tube for use with electronic counters of the type which require that any particular count be remembered for a suflicient time to allow for the count to be put in physical form, such as punched on a card.

In some electronic counters, it has been necessary to utilize two separate thyratron tubes, one of which was used for memory purposes and the other for read-out or punching purposes. At the time a count reading is desired, the memory thyratron is fired by the counter in cooperation with a suitable read-out pulse and thereafter remains in a conducting condition and places the required potential on the control electrode of the punching thyratron tube so that the punching thyratron is in condition to actuate the punching operation at any selected future time. These memory and punching circuits require an unnecessary number of thyratron tubes and unnecessarily complicated wiring circuits.

In order to overcome the disadvantages of the prior devices, a single gas filled tube having two anodes and a cathode is utilized to combine the memory and recording functions. In addition, this tube has a single control electrode which is actuated by an associated counter tube of an electronic counter in conjunction with a suitable read-out pulse, and this actuation causes conduction to take place between one of the anodes and the cathode. Conduction can then occur through the other anode to cathode at any future time as may be required for punching or other read-out function.

In order to utilize such a double purpose thyratron tube in connection with a bank of counting tubes representing a number of digits, a separate double purpose thyratron tube can be connected to each of the counting tubes and the counting tube representing the count on the bank of tubes at any particular time can be caused to actuate the correct double purpose tube in order to remember and thereafter punch the particular count. A digit emitter can be synchronized with the movement of a punch card so that the double purpose tube remembering the count will cause the correct digit to be punched on the card. By the use of such a circuit, any digital count can be taken from the counter and physically recorded at a later time.

It is therefore an object of this invention to provide a single thyratron tube which is an element of both the memory and recording circuits used in connection with electronic counters.

Another object of the invention is the provision of a double purpose gas filled tube having two separate conducting paths and a single control electrode for controlling the conduction along one of the paths.

A further object is to provide a double purpose thyratron tube which can be placed in a conducting condition by a counting tube of an electronic counter and thereafter permit the recording circuit to be actuated.

A still further object of this invention is to provide a 7 2,811,310 Patented Oct. 29, 1957 single thyratron tube which has a control electrode connected to the counter for placing the tube in conducting condition so that the tube can remember the count and thereafter permit this count to be later recorded.

A further object of this invention is to provide a punch ing and memory circuit which utilizes the double purpose thyratron tubes of this invention and which can be utilized in connection with a bank' of counting tubes so that the proper digital count on the counter tubes will be punched or otherwise recorded. 1

These and other objects not specifically enumerated above will becomerreadily apparent from the following specification and drawings in which: 1

Figure 1 is a schematic diagram of a double purpose thyratron tube which uses a single power source for both the memory and recording or punching circuits.

Figure 2 is a schematic diagram of a second embodiment of a'double purpose thyratron tube having completely independent power sources for the memory and punching circuits.

Figure 3 is a schematic diagram illustrating the manner in which the double purpose thyratron tubes are used in connection with electronic counters having a number of counting tubes;

Figure 4 is a perspective view of one physical construction of the double purpose thyratron tube illustrated in Figure 1.

The embodiment of the invention shown in Figure 1 illustrates the manner in which the double purpose thyratron tube 1 is controlled by a trigger tube 2 which is a component of an electronic counter. The complete trigger tube and its associated components, except for anodes 3 and 4, are notjshown in Figure 1 since this device is well known and has numerous modifications. It is only necessary that a binary configuration exist, in one of which conditions anode 4 is at a high potential and in the other configuration at a low potential. For the purpose ofillustration the high potential condition is considered to be the on condition of the trigger. The controlelectrode; of the double purpose thyratron is the grid 5. Itspote ntial is determined by the potentials of anode 4 and terminal 7 through the two resistors 6 and 8. Terminal 7 connects to a common read-out bus for all counterstages, and the combination of a high potential on anode 4,"alon g with a positive going pulse on terminal 7, is suflicient to cause conduction to occur in tube 1 from anode 9 to cathode 13 (connected with ground 14). Conduction is maintained from a supply voltage 10, such as +42 volts, through'a clearout switch 11 and a resistor 12. By the characteristics of gas filled tubes and the proper selection of voltages and components, conduction in tube 1 from anode 9 to cathode 13 will be maintained once it is initiated regardless of the subsequent changes in potentials of anode 4 or point 7, being solely reliant on continuation of a voltage supply from point 10. The tube. may be cleared out or deionized only by opening switch 11 at a suitable time. Having established conduction in tube 1 as the result of the coexistence of a read-out pulse and the proper configuration of the counter tube 2, the counter condition is then remembered until some future time when a read-out circuitis to be completed by conduction from anode 15 to cathode 13 of tube 1. In the figure shown, by way of example, the read-out circuit consists of' a potential source 16, a switch 17, and a punch magnet 18. The completion of the read-out or card, punching cycle is achieved inaccordance with the closure of switch 17. This is generally done in connection with atime sequence whereby the digits from O to, 9 have their switches sucthrough switch 30 and punching magnet 31.

established through the memory circuit portion of the tube from anode 9 to cathode 13. At the conclusion of the recording in punched card or other permanent form,

switch 11 which supplies memory anode current to the double purpose thyratron is opened, permitting the thyratron to be deionized, and then reclosed to permit the next read-out to ensue.

A physical embodiment of the tube 1 is illustrated in Figure 4 and like numerals illustrate similar parts. The electrode 5 is in the form of a casing for the tube and a constant potential is applied to the double anode 9. When sufiicient potential is placed on control electrode 5, conduction will take place between cathode 13 and anode 9, and when a recording potential is applied to anode 15, electrons will flow from cathode 13 past anodes 9 and to anode 15. A number of shields 19 are provided to direct the electronic flow within the tube. It is thus apparent that the physical embodiment illustrated in Figure 4 will function in the same manner as the tube 1 illustrated in Figure 1. This physical embodiment is similar in construction but not in function to the tube commonly designated as 2D21.

The embodiment illustrated in Figure 2 illustrates a double purpose thyratron tube having completely independent power sources for the memory and recording circuits. The control electrode 21 receives a potential from source 22, connected to both a trigger tube of the counter and a read-out source. A constant potential is applied by source 23 to anode 24 of the tube through switch 25 and resistance 26. When the control electrode 21 receives a sufiicient potential resulting from a read-out signal and the on condition of the trigger tube, tube 29 will be fired and conduction will continue between cathode 27 and anode 24. The tube 20 is therefore placed in a condition to remember the condition of the trigger tube. A second source 28 can apply a potential to anode 29 After the tube 20 is placed in conducting condition, the switch 39 can be closed and conduction will take place between anode 29 and cathode 32 to energize the magnet 31. Thus it is seen that the circuit through anode 24 will serve to remember the condition of the trigger tube and the circuit through anode 29 can be used to record this condition at some later time. The power source for these two circuits are completely independent so that the condition of one circuit can have no eflect on the condition of the other.

The double purpose thyratron tube can be used in parallel, as illustrated in Figure 3, to exclusively select and remember one of many digits in the electronic counter. The counter may contain a bank of trigger tubes representing the digits 0 to 9 inclusive. The counter tubes representing the digits 0, l and 9 are illustrated at A, B and I respectively in Figure 3 and it is understood that only the connections to these trigger tubes need be illustrated since the circuit for each additional digit could be applied to the circuit of Figure 3 in the manner illustrated for digits 0, 1 and 9. A constant potential, for example +42 volts, is applied at source 33 which is connected with anode 34 of tube 35, anode 36 of tube 37 and anode 38 of tube 39 through switch 40 and resistance 41. The cathodes 42, 43 and 44 of tubes 35, 37 and 39 respectively are continually connected to ground 45 through resistance 45. A read-out potential can be applied to source 47 which is connected to control electrodes 48, 49 and 50 through resistances 51, 52 and 53 respectively. Also, a high potential will be applied to the control electrode of the particular thyratron which is connected to the trigger tube representing the number in the counter bank at any particular time. If the read-out, signal is applied to source 47 at the time that the counter bank carries the digit 1, the potential applied to control elec- 4 trode 49 from source B and from the read-out signal will be sufiicient to fire tube 37 and will cause conduction between cathode 43 and anode 36 of the tube. This will be the only double purpose tube which will be fired by the read-out signal since all the other tubes will receive a low potential from the trigger tubes in the counter to which they are connected. After the tube 37 is fired, the tubes representing the digits 0 and 2 through 9 will be prevented from firing at a later time because the conduction through tube 37 will cause a potential drop in both the common anode resistor 41 and cathode resistor 46, and there will thereafter be iusufiicient anode to cathode potential in any of the unfired tubes to permit them to be made conducting and this condition will persist until conduction has been destroyed in the energized memory tube 37. Also, at the same time, the potential between the cathode and the control electrode of each of the unfired tubes will have increased as the result of the potential drop in resistor 46, and'this is another factor tending to prevent any tube other than 37 from being fired because of the lowered potential between the control electrode and the cathode. Therefore, after one of the double purpose tubes has fired, it will remember the particular count in the counter and this same tube can be used at a later time to record the count since it is impossible for the other double purpose tubes to remember any later count even though the counter continues to operate.

A digit emitter illustrated generally at 54 is utilized to record the countat a later time. This emitter has a wiperarm 55 which is supplied with a constant potential, such as 42 volts, at source 56. Also, the emitter has a series of ten contact posts 57 arranged in a circle about the axis of the wiper 55 and each one of these contact posts represents a digit from 0 through 9 as illustrated in Figure 3. Any type of well known recorder such as a card punching machine can be utilized to receive the particular count in the circuit. The wiper arm 55 will be synchronized with the movement of the recording system so that the digit contained in the emitter will be recorded at the proper time. For instance, the movement of Wiper arm 55 could be synchronized with the movement of a punch card so that the card will be in proper position when it receives a punching signal.

Each one of the posts 57 is connected to a second anode in the series of double purpose thyratron tubes. As illustrated in Figure 3, the posts corresponding to digits 0, l and 9 are connected to anodes 58, 59 and 60 of tubes 35, 37 and 39 respectively. 7 Also, a recording magnet 61 and a switch 62 are connected between the cathodes of each of the double purpose thyratron tubes and ground 63. When it is desired to make a recording of the count, the switch 62 will be closed and the wiper arm 55 will move from one contact post to another in the direction indicated by the arrow. When it contacts the post which is connected to the double purpose tube which has been previously fired for memor the punching circuit will be energized through the recording magnet 61. For instance, if tube 37 has been fired to represent the digit 1, the magnet 61 will be energized when the wiper contacts the post representing digit 1. Since the wiper arm will be synchronized with the movement of the recording device, the recording magnet 61 will be energized at the proper time to record the digit 1. As the wiper arm moves past the other digits, the recording magnet 61 will not be energized since the double purpose tubes representing the digits 0 and 2 through 9 will notbe in a conducting condition. Thus, only the digit 1 will be recorded on'the recording mechanism as the wiper arm makes a complete circle past the ten contact posts. it is obvious that only one digit can be recorded for each complete sweep of the wiper arm since when one tube has been fired'for memory, all of the other tubes are blocked.

After the count has been recorded, the switch 40 will be opened to remove the potential on the anode of the memory circuit for each double purpose tube. All of the 1 t be will he h placed i and willthereafter be ready .to receive the nextcount wh ch a is present in the counter at the time a read-out signal 1s anon-maduct sQndit Q applied to source 47 and switch 40 has been reclosed. When the next count is received, the memory circuit of the double purpose tube corresponding to this count will be energized and the punching circuit of the tube will be energized to record the count during movement of the digit emitter. Thus it is possible to obtain a series of successive readings from a counter which is recording successive counts.

It is understood that any type of recording mechanism can be used to record the counts remembered by the double purpose thyratron tubes and that the type of tube illustrated in Figure 2 could also be utilized in parallel to select and remember one of several digits. Also, a number of' circuits similar to that shown in Figure .3 can be included in a counter to record numbers of more than one digit during the movement of the recording device. Various modifications of this invention are contemplated and may be readily resorted to by those skilled in the. art without departing from the spirit and scope of the invention as hereinafter defined by the appended claims.

What is claimed is:

1. I A double purpose thyratron tube comprising memory and recording conduction paths including a common cathode, a first anode in said memory path and a second anode in said recording path, means for firing said thyratron tube at a selected time to cause conduction through said memory path and to immediately condition said tube for conduction through said recording path, and means for selectively energizing said recording path at any later time in order to record the condition of said thyratron tube.

2. In combination, a double purpose gas filled tube comprising first and second conduction paths containing first and second anodes respectively, an electrode in said tube positioned to control said first path, means for applying a potential to said electrode sufficient to fire said tube and cause conduction through 'said first path and to immediately condition said tube for conduction through said second path, means for thereafter applying at any selected time a potential to said second anode to cause conduction through said second path, and power means responsive to the conduction condition of said second path for indicating at said selected time Whether or not conduction is taking place in said first path, said potential applied to said second anode being insufficient to cause conduction through said second path in the absence of conduction through said first path.

3. In combination, a double purpose thyratron tube comprising first and second conduction paths, a control electrode in said tube for controlling said first path, means for applying a voltage to said electrode sufiicient to fire said tube and cause conduction in said first path and irn mediately conditioning said tube for. conduction through said second path, means comprising a source of constant potential for causing conduction in said second path at a selected time after said first circuit is conducting, and power means responsive to the conductive condition of said second path for indicating at said selected time whether or not conduction is taking place in said first path.

4. A double purpose thyratron tube comprising first and second conduction paths, an electrode for controlling conduction in said first path, means for applying a plurality of independent voltages to said electrode, said electrode permitting conduction in said first path at such time as said voltages are applied simultaneously, and means for causing conduction in said second path after said first circuit is conducting.

5. A double purpose gas filled tube comprising first and second anodes, a cathode and a control electrode, means for applying a voltage to said electrode sufiicient to fire said tube and cause conduction between said firstv anode and said gathode and means for thereafter applying a voltage to said second anode to cause conduction between said second anode and saidcathode.

6. In combination, a double purpose thyratron tube comprisinga memory. path and a recording path, said .memory path containing a first anode and a first cathode, .said recording, path containing a second anode and a second cathode, separate power supplies for. each of said ,paths, means forcompletely firing said thyratron'to cause conduction through said memory path at a selected time and to immediately condition said tube for conduction through said recording path, and means including a source of constant direct current potential. for later energizing said recording path at any selected time in order to record the conducting condition of said thyratron tube, said direct current potential being insuflicient to cause conduction through said second path in the absence of conduction through said first path.

7. Inhan electronic counter equipped with a number of counting tubes,'a double purpose thyratron tube having a cathode and first and second anodes, a control electrode connected 'to one of said counting tubes to receive a potential therefrom, means for applying a read-out potential to said control electrode sufiicient to fire said thyratron tube through said first anode when a potential is also received from said counting tube and means for selectively'applying a voltage to said second anode of said -thyratron tube when it is desired to record the conducting condition of said tube.

8. In an electronic counter equipped with a number of counting tubes, a thyratron tube having first and secondanodes and a control electrode, means for connecting said control electrode to one of said counting tubes, means for applying a constant potential to said first anode, means for applying a read-out voltage to said control electrode which is sufiicient to fire said, tube when a voltage from said counting tubeis also applied to said electrode and means forapplying a potential to said second anode in order to energize a recording circuit including-said second anode. V

9. In anelectronic counter equippedwith a number of counting tubes, a-thyratron tube having first and second anodes and'a control electrode, means for applying a constant potential to said first anode, meansfor applying a counting potential to said electrode from one of said counting tubes, means for applying an additional read-out potential to said control electrode at such time as a reading is desired, the sum of said counting potential and said read-out potential being suflicient to fire said thyratron tube to cause conduction through said first anode, means for selectively applying a voltage to said second anode after said tube had been placed in conducting condition to cause conduction to said second anode and recording means energized by conduction through said second anode.

10. In an electronic counter a number of counting :tubes representing individual digits, a number of thyratron tubes each having a control electrode connected to one of said counting tubes, each of said thyratrons having first and second anodes, means for supplying a constant potential to all said first anodes, means for supplying a read-out voltage to all said control electrodes sufficient to 'fire the thyratron connected to the counting tube representing the count at the time of ,said read-out signal, means for thereafter applying a potential to said vsecond-anodes to cause conduction through said second anode and a-recording mechanism in circuit with said second anode. i

11. In an electronic counter having a number of counting'tubes representing the digits sponding number of thyratron tubes each having a control electrode connected to one of said counting tubes to receive a counting potential when said counting tube represents the count in the counter, each thyratron hav :in'gfirst and second anodes included in first and. second 0 through 9, a. corre- 4 asiilsio circuits respectively, means for applying a constant potential to all of said first anodes, means for applying a r read-out voltage to all of said electrodes in order to fire the thyratron tube receiving a counting potential, means for applying a recording potential to all of said second anodes in order to energize said second circuit of said fired thyratron and recording means in said second circuit to record said count.

12. In an electronic counter defined in claim 11, said recording means being comprised of a number of contact posts each connected to said second anode of one of said thyratron tubes, a wiper movable past said contact posts in synchronism with the movement of said recording mechanism in order to apply a voltage on the second 1 anode of said fired thyratron at the proper time to record 7 the count.

13. In an electronic counter equipped with a number of counting tubes, a double purpose thyratron tube having first and second anodes, first and second cathodes and a control electrode, means for applying a constant potential to said first anode, means for connecting said control electrode to one of said counting tubes to receive a first voltage therefrom when a count is indicated by said counting tube, means for applying a second voltage to said electrode at any selected time, the sum of said first and second voltages being suflicient to fire said thyratron I tube between said first cathode and said first anode and means for applying a voltage to said second anode to cause conduction between said second anode and said second cathode.

' 14. A double purpose thyratron tube comprising a memory conduction path having an anode and a recording conduction path having an anode, a single cathode in I conducting relationship with both of said anodes, a control electrode for firing said tube and causing conduction between said cathode and the anode of said memory path at any selected time and means for applying a volt age to the anode of said recording path at a selected time after said tube has been fired to cause conduction in said recording path.

15. In an electronic counter equipped with a number i of counting tubes, a double purpose thyratron tube having first and second conduction paths, a control electrode for said first path and connected to one of said counting tubes to receive a potential therefrom, means for applying a read-out potential to said control electrode sufficient to fire said thyratron tube through said first path fwhen a potential is also received from said counting tube and means for thereafter selectively energizing said sec- 1 ond path of said tube when it is desired to record the conducting condition of said tube.

16. In an electronic counter equipped with a number of counting tubes, a double purpose thyratron tube having a memory conduction path and a recording conduc tion path, means for applying a potential to said memory path, a control electrode for said tube and connected to one of said counting tubes to receive a potential there- I from, means for applying a second potential to said electrode at any selected time, the sum of said first and sec- V, ond potentials on said electrode being sufficient to fire said thyratron tube through said memory path and means for applying a potential to said recording path to cause conduction therein at any selected time after conduction ing said thyratron tube at a selected time to produce a v conduction between the' cathode and the first anode for obtaining a flow of current through the memory circuit, a second anode in said tube and disposed relative to said first anode and said cathode to receive current flowing fromlsaid cathode towards said first anode upon the im- -position of. a proper -voltage on said second anode,'a recording circuit including the cathode and the second anode, and means for imposing a proper voltage on said ,second anode after' the production of a flow of current towards said first anode to produce a current through the recording circuit.

18. In combination, a thyratron tube, a first anode in said tube, a memory circuit including said first anode,

I an electrode disposed in said tube relative to said first anode to control the flow of current to said first anode in accordance with the voltage applied to said electrode, means for applying a potential to said electrode for producing a flow of current to said first anode and through said memory circuit, a second anode disposed relative to said first anode to receive current flowing towards said first anode upon the imposition of a proper potential on the second anode, a recording circuit including said second anode, and means for applying a proper potential on the second anode after the imposition of a current flow to the first anode to produce a flow of current to said second anode and through said recording circuit.

19. In combination, a thyratron tube, a cathode in said tube, a first anode in said tube, a memory circuit including said cathode and said anode, an electrode disposed in said tube between said cathode and said first anode, means for normally biasing the electrode with a potential relative to the potential on the cathode to prevent the firing of the tube for the flow of current towards the anode, means for introducing a signal to the electrode relative to the potential on the cathode to produce a flow of current from the cathode to the anode and through the memory circuit, a second anode disposed in said tube relative to the first anode to receive current flowing towards the first anode upon the imposition of a proper voltage upon the second anode, a recording circuit including said cathode and said second anode, and means for applying a proper voltage on the second anode 7 after the flow of current through the memory circuit to produce a fiow of current to thesecond anode and through the recording circuit.

20. In combination, a plurality of counting means each adapted to indicate different information such as numerical information, a plurality of thyratron tubes each associated with a different counting means in the plurality, an electrode in each thyratron tube, an anode in each thyratron tube and disposed relative to the electrode in the tube to receive current upon the imposition of a proper voltage upon the electrode, means connected to each anode to form separate memory means for the storage of information from the associated counting means upon the flow of current to the anode, means for connecting each counting means to the electrode in the associated thyratron tube to apply a counting voltage to one of the electrodes, means for simultaneously applying a read-out voltage to the electrodes of the thyratron tubes in the plurality to produce a flow of current to the anode of the tube receiving the counting potential on its electrode, a second anode in each of said tubes disposed relative to the first anode, the second anode in the energized tube receiving current flowing towards the first anode upon the imposition of a proper voltage upon the second anode, means for applying the proper voltage to the second anode of the energized tube upon the flow of current to the first anode, and means connected to the second anode of the energized tube for providing a record of the count stored in the memory means.

21. In combination, a plurality of counting means each adapted to indicate different information such as numerical information in accordance with an output voltage, a plurality of thyratron tubes each having an electrode connected to a different one of the counting means in the plurality, a first anode in each thyratron tube disposed relative to the electrode to receive a current through the tube upon the imposition of a proper voltage on the electrode, means for applying a read-out potential to each voltage from the associated counting means, memory means connected to the anode of each tube to receive the flow of current through the energized tube, a second anode in each tube and disposed relative to the first anode to receive current flowing towards the first anode upon the imposition of a proper voltage on the second anode, means for sequentially applying the proper voltage to the second anode of successive tubes in the plurality to produce a flow of current to the second anode in the energized thyratron tube, and means for providing a record of the remembered information in accordance with the flow of current to the second anode of the energized thyratron tube.

22. In combination, a plurality of thyratron tubes, a cathode in each thyratron tube, an electrode in each thyratron tube, a first anode in each thyratron tube and disposed relative to the cathode and the electrode to receive current from the cathode upon the imposition of a proper voltage difference between the cathode and the electrode, a plurality of counting means each adapted to apply a potential between the cathode and the electrode of a different thyratron tube upon the reception of electrical signals by the counting means, means for simultaneously applying a potential between the cathode and the electrode of the different thyratron tubes to energize the tube receiving a potential from its associated counting means, circuit means including the cathode and the first anode in each thyratron tube to maintain the flow of current through the energized tube, a second anode disposed in each tube relative to the first anode to receive current flowing towards the first anode upon the imposition of a proper voltage on the second anode, switching means for sequentially applying the proper voltage to the second anode of the different tubes to produce a flow of current to the second anode of the energized tube, and circuit means including the cathode and the second anode in each thyratron tube for providing a record of the flow current to the second anode in the energized tube.

23. In combination, a gas filled tube, a first anode in said tube, a first circuit including said first anode and means for applying a potential thereto, an electrode disposed in said tube relative to said first anode to control the flow of current to said first anode in accordance with the voltage applied to said electrode, means for applying a potential to said electrode for producing a flow of current to said first anode and through said first circuit, a second anode in said tube, a second circuit including said second anode, means for applying a potential on said second anode at any selected time after the imposition of a current fiow to the first anode to produce a flow of current to said second anode, the potential applied to said second anode being insufiicient to cause conduction through said second circuit in the absence of conduction through said first circuit and said tube being immediately conditioned for conduction through said second circuit upon the production of current flow through said first circuit, and means responsive to the conductive condition of said second circuit for manifesting at said selected time whether or not conduction has been initiated in said first circuit.

24. In combination, a thyraton tube, a first anode in said tube, a first circuit including said first anode, a second anode in said tube, a second circuit including said second anode, a single cathode in said tube in conducting relationship with both of said anodes, a control eletcrode in said tube for firing said tube and causing conduction between said cathode and the anode of said first circuit at any selected time, and means for applying a voltage to the anode of said second circuit at a selected time after said tube has been fired to cause conduction in said second circuit.

References Cited in the file of this patent UNITED STATES PATENTS 1,697,281 Meyer Jan. 1, 1929 1,932,373 Lems Oct. 24, 1933 2,034,756 Hansel! Mar. 24, 1936 2,299,229 Hall Oct. 20, 1942 2,408,004 Slack Sept. 24, 1946 2,470,920 ColSOn May 24, 1949 

